Braking and tension roll



May 10, 1966 G. .1. PRAGER BRAKING AND TENSION ROLL Filed Oct. 5, 1965IN VEN TOR. p/Wef United States Patent O 3,250,488 BRAKING AND TENSIONROLL George J. Prager, Rosemont, Pa., assignor to Beloit EasternCorporation, Downingtown, Pa., a corporation of Delaware A Filed Oct. 3,1963, Ser. No. 313,684 2 Claims. (Cl. 242-754) The present inventionrelates to a web tension control means and particularly to an improvedmethod and mechanism for maintaining a constant tension in a travelingweb from an unwinding paper roll.

In an unwinding mechanism a web is continually drawn off of a supplyroll for an operation on the web such as a-slitting, coating or surfacetreating operation and it is essential that the tension in the travelingweb be maintained constant and be controlled across the full Width ofthe web. The unwinding machines are continuous with a fresh roll beingplaced in the machine as the unwinding roll is expiring and a dyingsplice being made to splice the lead end of the web from the fresh rollto the traveling surface of the web of the expiring roll. Therequirements for constant tension across the Width of the web continueall during the unwinding operation including during the time of makingthe splice.

Web tension control has been conventionally done by applying a brakingtorque to the unwinding roll. However, the unwinding roll is continuallychanging in diameter so that in order to maintain a constant tension inthe web the braking torque must be constantly changed. In other words,as the diameter of the unwinding roll decreases the torque must beincreased, and the speed of rotation of the unwinding roll inrevolutions per minute continually changes while maintaining constantweb surface speed. Attempts to overcome the difliculties have includedbrakes operating on variable size drums, the use of dance rolls, andother devices all of which require a mechanism over and above simplebraking devices and which cannot obtain constant tension in a simplemanner.

It is accordingly an object of the present invention to provide a webunwinding mechanism capable of delivering a traveling web at uniform webtension across the Web at uniform speed without requiring complexmechamsm.

A further object of the invention is to provide an unwind mechanismutilizing a method and apparatus for controlling the tension of the webby providing a tensioning force directly to the surface of the travelingweb, utilizing the advantage of the constant speed of travel of the weband applying a constant braking force theret0.

A more broad object of the invention is to provide a tension controldevice for maintaining a constant tension across the width of atraveling web for utilization in 'various types of devices embodying atraveling web moving at constant web speed. It will be understood thatwhile the principles of the invention may he utilized and are applicablein various environments for the purposes above described, the principlesare particularly well suited to use in an unwinding mechanism and have aspecial coaction therewith in the combinations set forth so that thedisclosure and description of the invention will be presentedprincipally in connection with an unwinding machine.

The invention contemplates providing a mechanism for controlling thetension of a web being paid otf an unwinding roll having an unwindingroll support stand with a pull roll receiving the web traveling from theunwinding roll and drawing it forwardly, having a roll brake on theunwinding roll on the support stand for preventing overrunning oftheunwinding roll and maintaining a slight control in the web, andadditionally having a web brake with a tension control web roll wrappedby the web and with a constant running torque brake connected to the webroll for maintaining a predetermined tension in the web.

Other objects, advantages, and features will become more apparent withthe teachings of the principles of the invention in connection with thedisclosure of the preferred embodiments thereof in the specification,claims and drawings, in which:

FIGURE 1 is a side elevational view shown largely in schematic form ofan unwinding mechanism constructed and operating in accordance with theprinciples of the present invention; and

FIGURE 2 is a fragmentary schematic side elevational view of a web brakeof modified form.

On the drawings:

As illustrated in FIGURE 1, an unwinding web W travels at a constantspeed from a roll on an unwinding stand l0. The tension of the web W ismaintained constant across the web by a web brake roll 11 in frictionalengagement with the web. The web travels through a treatment zone 12which may be a web slitter, coater, surface finisher or other treatmentmechanism such as is known to the art of paper making and converting,and passes through rolls 13 and 14 of a pull stack and over rolls 1Sonto a Wind up roll 16. The wind up roll is driven by a suitablemechanism to wind up the paper Web which is moved forwardly at constantspeed by pull rolls such as that of the pull stack rolls 13 and 14.

The Web is maintained in frictional contact with the web brake roll 11by a wrapping roll 17 positioned to preferably wrap the web around themajor arc of the brake roll 11. A pre-selected constant torque isapplied to the web brake roll 11 by a brake 18. The brake 1S may be' ofvarious desirable types capable of applying a constant torque, such asan eddy current brake with a regenerative motor, or other types Aofbrakes such as an air brake, an hydraulic brake, or electric brake maybe employed. In other words, the brake applies a constant force to thebrake roll 11 so that a constant braking force is applied to the web Wwhich is wrapped over the brake roll 11.

The roll 11 has a web engaging surface of a high friction material suchas rubber. I have discovered that polyurethane provides unforeseenresults on the surface of the braking roll, and has an unusualfrictional effect on a traveling paper web. Therefore, the preferredform of braking roll will have a polyurethane surface. In someenvironments Where a very low tensile strength web is to rbe handled webbraking rolls of other surfaces may be employed such as a polished steelsurface which will permit slippage of the web without web breakage ifconditions change suddenly. Also, the amount of surface area of the webbraking roll 11 wrapped by the traveling web W may be changed inaccordance with the tensioning force to be applied to the Web with theangle of wrap being diminished in cases Where the Ltension on the webapproaches the ultimate tear stress of the web so that slippage canoccur in case of sudden change of conditions. Under normal operatingcircumstances With a strong web, utilizing a polyurethane covered -rollno slippage will occur and positive web tension control is obtainedcompletely across the web at constant we'b speed Without having tocontend with the variables caused by diminishing roll diameters such asmust be encountered if tensioning is obtained by applying forces to theIunwinding roll. Attempts to control tension in unwinding webs haveincluded, in addition to applying a braking force directly to theunWinding roll, applying tapes or bands to the surface of the roll, andthe methods are limited to uncoated stocks and low tension factors inorder to prevent s-cufling and glazing of the sheet.

The present arrangement contemplates using :a roll brake in order toprevent overrunnning of the parent roll as it unwinds and in order tostop the rotation of the core of the expired roll after the splice hasbeen made. As shown on the drawing, an expiring roll 19 is supported ona turret 21 on a stand 25. Connected to the support for the roll 19 is abrake and drive 20. During unwinding a slight brake force is appliedmerely to provide a control tension to the web between the unwindingroll and the web braking roll 11. For example, a light tension of l to 3pounds is applied to the web approaching the web ybraking roll 11. rDhetension in the web between the braking roll and the pull rolls 13 and 14can be controlled by the variable brake 18 and, for example, a constanttension of pounds may be applied to the web.

The turret 21 is arranged with a guide roll 23 on an arm 22 for guidingthe web to the splicing and cutting device 28. Carried at the other sideof the turret 21 is a fresh roll 26 also provided with .a brake anddrive 27. As the Poll 19 begins to expire, the fresh roll 26 is drivenin rotation until its surface speed is the same as the speed of thetraveling web W, and at that time the lead end of the second web on thesecond or fresh roll 26 is spliced to the surface of the web W.

For forming the splice, a splice roll 32 is forced against the web Wcarrying it against the surface of the fresh roll 26 and the splice ismade usually by splice tapes having pressure sensitive adhesive locatedon the lead end of the web on the fresh roll 26.` The first web is thencut by a cutter 34. The :splice roll and cutter carried on a pivotal arm30 are pivotedvat 31, and the arm is pivoted by an air piston andcylinder 33. The cutter 34 is operated lby an air piston and cylinder35.

If a fresh roll 26 is to be unwound in the direction opposite that shownby the arrow on the roll 26, the turret 21 will be swung in thedirection opposite that shown by the arrowed line appearing on theturret 21.

More particularly, prior to loading the fresh roll 26 into the turret,the roll 19 will be in the position now occupied by roll 26 in FIGURE 1.The fresh roll 26 is then loaded into the turret and the turret is swungin either rotational direction depending upon the direction in whichroll 26 i-s to be unwound, bringing the roll 26 in the position in whichit is shown in FIGURE l. If it is swung in the direction indicated bythe arrowed line on the turret 21, the elements will take the posit-ionshown in FIGURE 1, and if the turret is swung in the opposite directionthe web W will 4be guided by the roll 24 and the splicing mechani-sm 29will be employed. This mechanism i-s substantially the same as thesplice mechanism 28 and includes a splice roll 36 carried on an arm .40which is pivoted on its pivotal support 31 by an air piston and cylinder37. Also carried on the arm 40 is a cutting knife mechanism l33 operatedby an air piston and a cylinder 39.

In operation the web W will be paid off of the unwinding roll, brakedslightly by the brake mechanism 20. The web moves forwardly at aconstant speed drawn by the pull rolls 13 and 14 and fa constant tensionis maintained across the web by the web braking roll 11. A predeterminedconstant braking torque is applied to the roll 11 by the :brake 18 andthe tension in the web will remain constant in its travel through theweb treatment zone 12. When the roll 19 expires a splice is made tosplice the lead end of the web from the roll 26 to the web W, .and thefresh web will then travel over the braking roll 11 and throughout the:splicing operation and with the transition in webs, constant tensionwill be maintained without requiring a critical control of the brakingfonce applied by the roll brakes and 27 and the splice will take placewithout :any adverse affect to the uniform tension in the web as itpasses through the treatment zone 12.

FIGURE 2 illustrates another form of engagement between the braking rolland the web wherein a web brak-ing roll 41 frictionally engages a web Wwhich is held against the roll by a pinch roll 42 forming a nip Nwiththe braking roll 41. The :overall frictional force between the web W andbraking roll 41 can be varied by varying the nip pressure by suitablemechanisms shown schematically by the arrowed line 43. This arrangementmay also be employed where the web is handled which ha-s a tension limitclose to the applied operating tension.

Thus, it will be seen that I have provided a traveling web tensioncontrol mechanism which meets the objectives, advantages and featuresabove set forth, and which is well suited to all phases of the paperindustrys unwinding loperations including paper making, processing,finishing and printing. The mechanism controls tension across the fullwidth of the sheet at a point where the sheet speed is constant insteadof contending with speed changes due to decreasing diameters. This alsonecessitates a smaller `range off control requirements and permitsproviding braking mechanism which can operate at optimum efficiency andalso permits using a braking mechanism of less complex nature and lessexpensive construction. The unique frictional coaction between latraveling fpaper web and the polyurethane roll reduces slippage tosubstantially zero and highly critically finished paper webs may be`handled without any adverse effect to the surface qualities. Thebraking force is applied to the web after it leaves the unwinding rolland constant tension is maintained eliminating problems heretoforeencountered in the rolls being unwound and in the wind up roll.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed, but coversall modifications, changes and alternative constructions and methodsfalling within the scope of the principles taught by the invention.

I claim as my invention:

1. An unwind mechanism for continually delivering a traveling webcomprising,

a first unwind roll support for a roll having a first web unwoundtherefrom,

a second unwind roll support for a fresh roll having a second web to bespliced to the first while it is traveling,

a pull roll receiving the first web,

a tension control web braking roll frictionally engaging the surface ofsaid first roll between said supports and said pull roll,

a brake means having a constant running torque oonnected to said webbraking roll for maintaining a predetermined tension in the web,

means for driving said second roll for bringing the surface speed to thespeed of said first web,

la roll brake for said first roll preventing overrun and stopping theroll after splicing the second web to the first,

and a splice means for splicing the second web to the first while it istraveling and .cutting the first web so that said web breaking roll willuniformly continue to apply constant braking force sequentially to bothsaid first and second webs without change in tension to the pull roll.

2. An unwind mechanism for continually delivering a traveling webcomprising,

an unwind stand having a turret thereon mounted on a horizontal taxis onthe stand with a first support for an unwinding roll having a first webbeing paid olf the first roll and having a second support for a secondfresh unwinding roll having a second web to be spliced to the surface ofthe first web,

said turret being rotatable through positions for loading with a freshroll and removing an empty core from an expired roll,

a rst cutting and splice means positioned above the second roll in asplice position for splicing the second web to the rst web,

a ysecond cutting and splice means positioned below the second roll insaid splicing position for splicing the second web to the rst web whensaid second roll is -rotating in an opposite direction,

a Wind up roll,

guide rolls guiding the Web to said Wind up roll with lsaid guide rollsand Wind up roll drawing the web forwardly,

means defining a web treatment zone between the un- Winding roll and theWind up roll,

a tension control web b-raking roll having a surface of polyurethanepositioned between said treatment zone and the unwinding roll,

a` Web Wrapping roll positioned to wrap the Web around a major farc ofsaid web braking roll,

a constant torque brake connected to said web braking roll for applyinga constant tension to the traveling web ata constant speed of travel,

and roll brakes connected to 4said irst and second rolls for preventingoverrun of the rolls and stopping the rolls after they have becomeunwound,

said constant torque brake being lcontrollably variable for varying thetension in the web and obtaining a predetermined constant tension duringWeb travel.

References Cited by the Examiner UNITED STATES PATENTS 1,263,419 4/1918James 242-752 2,177,489 10/ 1939 Jamieson 242-45 2,485,75 7 10/ 1949Michel d 242-75 .4 2,707,083 4/ 1955 Kohler 242-75 .2 2,728,973 1/ 1956Kummel 28-1 A 2,995,768 8/ 1961 Tomberg 242-7544 3,08 5,762 4/ 1963Subklew 242-58 FOREIGN PATENTS 745,224 2/ 1956 Great Britain.

STANLEY N. GILREATH, Primary Examiner.

MERVIN STEIN, Examiner.

D`l E. WATKINS, Assistant Examiner.

1. AN UNWIND MECHANISM FOR CONTINUALLY DELIVERING A TRAVELING WEBCOMPRISING, A FIRST UNWIND ROLL SUPPORT FOR A ROLL HAVING A FIRST WEBUNWOUND THEREFROM, A SECOND UNWIND ROLL SUPPORT FOR A FRESH ROLL HAVINGA SECOND WEB TO BE SPLICED TO THE FIRST WHILE IT IS TRAVELING, A PULLROLL RECEIVING THE FIRST WEB, A TENSION CONTROL WEB BRAKING ROLLFRICTIONALLY ENGAGING THE SURFACE OF SAID FIRST ROLL BETWEEN SAIDSUPPORTS AND SAID PULL ROLL, A BRAKE MEANS HAVING A CONSTANT RUNNINGTORQUE CONNECTED TO SAID WEB BRAKING ROLL FOR MAINTAINING APREDETERMINED TENSION IN THE WEB, MEANS FOR DRIVING SAID SECOND ROLL FORBRINGING THE SURFACE SPEED TO THE SPEED OF SAID FIRST WEB, A ROLL BRAKEFOR SAID FIRST ROLL PREVENTING OVERRUN AND STOPPING THE ROLL AFTERSPLICING THE SECOND WEB TO THE FIRST, AND A SLICE MEANS FOR SLICING THESECOND WEB TO FIRST WHILE IT IS TRAVELING AND CUTTING THE FIRST WEB SOTHAT SAID WEB BREAKING ROLL WILL UNIFORMLY CONTINUE TO APPLY CONSTANTBRAKING FORCE SEQUENTIALLY TO BOTH SAID FIRST AND SECOND WEBS WITHOUTCHANGE IN TENSION TO THE PULL ROLL.